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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_Icedid_GZIP_LDR_202104

2021 initial Bokbot / Icedid loader for fake GZIP payloads

MalwareIcedidSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Thomas Barabosch, Telekom Security
Date
2021-04-12
Modified
2023-01-27
Score / Quality
75 / 85

What this rule detects

2021 initial Bokbot / Icedid loader for fake GZIP payloads

Associated malware family: Icedid.

Targets: Windows PE.

It defines 11 patterns (11 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

mal-icedid-gzip-ldr-202104.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_Icedid_GZIP_LDR_202104 : FILE
{
	meta:
		description = "2021 initial Bokbot / Icedid loader for fake GZIP payloads"
		author = "Thomas Barabosch, Telekom Security"
		id = "fbf578e7-c318-5f67-82df-f93232362a23"
		date = "2021-04-12"
		modified = "2023-01-27"
		reference = "https://www.telekom.com/en/blog/group/article/let-s-set-ice-on-fire-hunting-and-detecting-icedid-infections-627240"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/crime_icedid.yar#L14-L40"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "7a7cc6c7dcbf43bace6a1f259af38560327c34386517e719ad81068b2d9b6659"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$internal_name = "loader_dll_64.dll" fullword
		$string0 = "_gat=" wide
		$string1 = "_ga=" wide
		$string2 = "_gid=" wide
		$string4 = "_io=" wide
		$string5 = "GetAdaptersInfo" fullword
		$string6 = "WINHTTP.dll" fullword
		$string7 = "DllRegisterServer" fullword
		$string8 = "PluginInit" fullword
		$string9 = "POST" wide fullword
		$string10 = "aws.amazon.com" wide fullword

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 5000KB and ( $internal_name or all of ( $s* ) ) or all of them
}

Strings (11 patterns)

IdentifierTypeValueModifiers
$internal_nametext"loader_dll_64.dll"fullword
$string0text"_gat="wide
$string1text"_ga="wide
$string2text"_gid="wide
$string4text"_io="wide
$string5text"GetAdaptersInfo"fullword
$string6text"WINHTTP.dll"fullword
$string7text"DllRegisterServer"fullword
$string8text"PluginInit"fullword
$string9text"POST"wide fullword
$string10text"aws.amazon.com"wide fullword

Condition

uint16( 0 ) == 0x5a4d and filesize < 5000KB and ( $internal_name or all of ( $s* ) ) or all of them

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • The file must be smaller than 5000KB (a cheap guard that skips large files).
  • All patterns in ( $s* ) must match.
  • All patterns in the rule must match.
  • Pattern $internal_name must be present.

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References

Licence & attribution

Author: Thomas Barabosch, Telekom Security

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: fbf578e7-c318-5f67-82df-f93232362a23

Tags:FILE

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